催化学报 ›› 2023, Vol. 47: 138-149.DOI: 10.1016/S1872-2067(23)64416-X

• 论文 • 上一篇    下一篇

CO2作为化学品原料的高效利用途径: 与烷烃耦合反应

危长城a,b, 张雯娜a, 杨阔a,c, 柏秀a,d, 徐舒涛a, 李金哲a,*(), 刘中民a,b,*()   

  1. a中国科学院大连化学物理研究所, 洁净能源国家实验室, 低碳催化技术国家工程研究中心, 辽宁大连116023
    b中国科学院大学, 北京100049
    c大连理工大学化工学院催化化学与工程系, 精细化工国家重点实验室, 辽宁大连116024
    d大连理工大学张大煜化学学院, 辽宁大连116024
  • 收稿日期:2023-02-13 接受日期:2023-02-16 出版日期:2023-04-18 发布日期:2023-03-20
  • 通讯作者: *电子信箱: lijinzhe@dicp.ac.cn (李金哲),liuzm@dicp.ac.cn (刘中民).
  • 基金资助:
    国家自然科学基金(21991093);国家自然科学基金(21991090);国家自然科学基金(22288101)

An efficient way to use CO2 as chemical feedstock by coupling with alkanes

Changcheng Weia,b, Wenna Zhanga, Kuo Yanga,c, Xiu Baia,d, Shutao Xua, Jinzhe Lia,*(), Zhongmin Liua,b,*()   

  1. aNational Engineering Research Center of Lower-Carbon Catalysis Technology, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
    bUniversity of Chinese Academy of Sciences, Beijing 100049, China
    cState Key Laboratory of Fine Chemicals, Department of Catalysis Chemistry and Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China
    dZhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, Liaoning, China
  • Received:2023-02-13 Accepted:2023-02-16 Online:2023-04-18 Published:2023-03-20
  • Contact: *E-mail: lijinzhe@dicp.ac.cn (J. Li),liuzm@dicp.ac.cn (Z. Liu).
  • Supported by:
    National Natural Science Foundation of China(21991093);National Natural Science Foundation of China(21991090);National Natural Science Foundation of China(22288101)

摘要:

CO2作为碳资源的规模化高附加值利用是实现其减排的重要方向. 然而, 由于其热力学稳定, 以CO2为原料高效转化为大宗化学品一直是一个巨大的挑战. 工业上普遍以富氢的石脑油为原料生产相对缺氢的烯烃和芳烃产品, 但其存在原料和目标产品之间的碳氢不平衡问题. 理论上, 采用CO2与富氢的烷烃耦合, 可以改善二者的平衡关系, 提高目标产物选择性, 同时实现CO2资源化利用. 已有研究采用CO2与烷烃反应, 将CO2转化为CO并减少氢气的生成, 但CO2的碳原子没有进入烃类产物中. 本文系统研究了酸性分子筛催化的CO2与烷烃耦合反应, 大幅提高了芳烃选择性, 证实部分CO2中的碳原子直接进入了芳烃产品中.

本文以H-ZSM-5为催化剂, 对比研究了正丁烷、正戊烷和正己烷在He和CO2气氛中的转化反应, 并详细研究了反应温度、CO2/n-butane比例、接触时间以及分子筛酸量等条件对耦合反应的影响. 结果表明, CO2的引入可大幅促进芳烃的生成, 同时甲烷和乙烷等小分子烷烃的生成受到抑制. 在优化反应条件下, CO2/n-butane比例为0.475时, CO2n-butane转化率分别可达17.5%和100%, 芳烃选择性高达80%. 使用13C同位素标记的CO2n-butane进行耦合反应, 发现芳烃产物中含有部分13C同位素标记的碳原子, 表明这部分碳原子来自CO2中的碳. 对耦合反应后的催化剂进行溶积碳并采用色质谱分析, 发现大量甲基取代的内酯和甲基取代的环烯酮等含氧物种. 同位素标记实验结果表明, 这些含氧中间体由CO2与烃类耦合转化生成. 通过设计实验验证了反应途径, 即CO2与碳正离子反应得到环内酯, 环内酯进一步转化为甲基环烯酮, 甲基环烯酮转化为芳烃产物. 提出了H-ZSM-5催化CO2与烷烃耦合反应的机理, 并采用密度泛函理论计算了耦合反应机理各步骤的能垒, 结果验证了耦合反应机理的可行性. 综上, 本文提出的耦合反应为CO2碳资源的大规模直接利用提供了一条有效的途径, 具有广阔的应用前景.

关键词: 二氧化碳转化, 轻质烷烃, 芳烃, 催化, 分子筛

Abstract:

The most promising method to eliminate CO2 is to find large-scale and value-added applications of CO2 as a carbon resource. However, the utilization of CO2 as feedstock for basic chemicals has long been a great challenge owing to its high thermodynamic stability. Herein, we report the coupling conversion of CO2 with light alkanes over the HZSM-5 zeolite with much higher aromatic selectivity than light alkanes as the only reactant. A CO2 conversion of 17.5% and n-butane conversion of 100% with aromatic selectivity of 80% could be achieved by the coupling reaction at the CO2 to n-butane ratio of 0.475, in which CO2 not only acted as an agent for balancing hydrogen in the reaction but also partly (~25%) incorporated into the aromatic products. Methyl-substituted lactones (MLTOs) and methyl-substituted cycloalkenones (MCEOs) were identified as key intermediates during the coupling reaction. 13C isotope labeling experiments, 13C solid-state NMR, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory (DFT)calculations revealed that CO2 could react with carbonium ions generated from alkane cracking to form MLTOs, which could further get converted into MCEOs, thus generating aromatic compounds. This coupling reaction provides guidance for the direct utilization of CO2 to produce value-added chemicals with the simultaneous transformation of light alkanes.

Key words: CO2 utilization, Light alkanes, Aromatics, Catalysis, Zeolite